US-B2-U.S. Pat. No. 8,907,760, discloses a remote access system in which a three-dimensional low-frequency (3D-LF) antenna and a HF antenna are used. The 3D-LF antenna includes three coils each oriented relative to X, Y and Z axes that define a Cartesian coordinate system for a three-dimensional space, whereas the HF antenna is oriented along one of the axes of the LF coils, in the same antenna package as the 3D-LF antenna. In this patent, the HF antenna is connected close to one of the LF coils, e.g. by winding the HF antenna around the outside of the LF coils, duly separated, or by placing the HF antenna below and/or above the LF coil (in particular the LF coil located parallel to the Z axes). The 3D-LF antenna is configured to be used in connection with a LF signal of between 3 KHz and 300 KHz while the HF antenna is configured to be used in connection with an HF signal between 3 MHz and 30 MHz.
JP 2015080147 A discloses a dual-band antenna device for a keyless entry system, comprising a single coil antenna wound around a magnetic core and a second planar coil antenna disposed on an insulating substrate, wherein the second planar coil antenna is arranged above the first coil antenna, and wherein the first single coil antenna and the second coil antenna are isolated from each other by a ferromagnetic material sheet. This patent then integrates a RF antenna (310 MHZ for remote opening/closing) of the control of the key in a PKES with an antenna LF for Wake up or RFID. Although the dual-band antenna device of this Japanese patent application can work as a LF and as a HF antenna, unlike the proposed antenna device, it cannot work at a frequency range comprised between 3 and 30 MHz when working as a HF antenna. Moreover, the HF antenna of this dual-band antenna device is not arranged on an electrically insulating replaceable cap, and so not allowing different performances of the HF antenna.
WO2015/022000 A1 discloses an antenna device with several winding wound around a magnetic core and an adaptor arranged over the magnetic core and having an external surface comprising electrically conductive platings following a specific PCB layout and connected to electrically conductive elements coupled to said windings.
An object of the invention is to provide an improved inductive antenna device for both functionalities (HF and LF communications) saving components and physical space. In particular according to the solution of this invention the HF antenna is integrated in an element, a cap, that provides protection of the elements of the LF antenna (upper part and sides) and which can be easily replaced allowing different embodiments of the HF antenna independently of the arrangement of the LF antennas.